1. Field of the Invention
This invention relates generally to the field of fluid handling and liquid chromatography. In particular, the invention is directed toward a novel sanitizable rotary valve that may be used in conjunction with liquid chromatographic columns and sanitary liquid handling systems to separate and/or purify biological macromolecules of importance to the pharmaceutical industry.
2. Description of the Prior Art
Rotary valves have been used for multiple fluid distribution in many different variations. For instance, U.S. Pat. No. 4,808,317 (Berry et al.) is directed to a method and device including a rotary valve for continuously contacting fluids with solid particulates. The design of this fluid distribution valve also allows simulated moving bed ("SMB") counter-current operation. In general, the device operates as follows. A plurality of inlet conduits are provided at the top of a feed box for the purpose of introducing fluid streams into the device for treatment, and a corresponding plurality of outlet conduits are provided at the bottom of the discharge box for removing treated fluid streams. Separator compartments are located so that they rotate past the fluid ports. In normal operation the separator compartments contain a resin or other adsorbent particulate bed which is then sequentially contacted with each fluid stream through the upper and lower timing crown stator ports. Details of the operation of the rotary valve are presented in the '317 patent's FIGS. 5 and 7 through 9. As can be seen from these figures, the rotor and stator must be fully disassembled for cleaning and no provision has been made for sanitizing the contact faces of the rotor and stator surfaces.
U.S. Pat. No. 2,985,589 (D. B. Broughton et al.) is directed to a process and apparatus for continuous simulated counter-current flow to and from the several inlets and outlet streams in relation to beds of solid sorbent. A rotary valve is described for connecting the inlet and outlet fluid streams to the adsorbent bed columns. The process and apparatus are demonstrated by separating a mixture of normal and isohexanes into a stream of relatively pure N-hexane and a secondary product of isohexane. The apparatus comprises a series of 12 beds containing molecular sorbent. The rotary valve used is not sanitizable, and there is no indication that a sanitizable valve face was contemplated.
U.S. Pat. No. 3,268,604 (D. M. Boyd, Jr.) is directed to a fluid flow control system for simulated moving bed processes which include a rotary valve. A multi-port rotary distributing valve is shown in FIG. 1, which is capable of being connected to 24 fluid transfer lines. The valve does not have any sanitizing feature.
U.S. Pat. No. 4,409,033 (LeRoy) is directed to a simulated moving bed separation process for high capacity feed streams, and incorporates a fluid distribution means comprising a rotary valve. Again, no sanitizable aspects are disclosed.
Known non-rotary sanitizable valves include Mieth, U.S. Pat. Nos. 4,757,834 and 4,687,015; and Dolling 4,191,213. Also known are rotary valves granted to Ringo, U.S. Pat. No. 2,706,532 and Pruett, U.S. Pat. No. 3,451,428. The latter two patents disclose no sanitary flushable design.
U.S. Pat. No. 4,921,015 (Sedy) is directed to a rotary vacuum valve having two annular continuous pressurized chambers formed in the sealed face of the rotor. In each chamber are a pair of annular U shaped elastomeric Teflon.TM. seals expanded by an expansion spring positioned concentrically within the open sides of the seals. These seal assemblies are known as spring-energized TFE lip seals. The stator and rotor move slightly apart upon the application of high pressure to the stator, the lift being sufficient so that the spring-loaded TFE lip seals have a slight contact with the top of the ring, allowing the seal faces to run dry. Thus the arrangement presents a dry low friction seal between the two valve members. No sanitizable or flushable means are provided.
U.S. Pat. No. 4,625,763 (Shick et al.) is directed to a disc-axial multi-port valve for accomplishing the simultaneous interconnection of a plurality of conduits. The valve is comprised of a stator and a rotor, both being comprised of two sections, one being cylindrical and the other being disc-like. FIG. 1 discloses a peripheral seal element 94 retained in a grove in the rotor discular element and urged against the stator transfer face by springs such as 92t. Any fluid leaking from the transverse volume will be retained by this barrier. In addition, in order to prevent cross contamination among the conduits which are interconnected, a flushing fluid may be passed through the transverse volume. Referring again to FIG. 1, flushing fluid may be provided to transverse volume 90 via conduit 95. However, no arrangement is made for pulling apart the faces of the rotor and stator in order to sanitizably flush the faces.
Aseptic diaphragm valve construction, or sanitary valves, are known in the art. These valves are used for aqueous fluids containing or capable of containing microorganisms, or for handling of foods, beverages, or of materials being made into pharmaceuticals or the like. For example, Hoobyar et al. U.S. Pat. No. 5,152,500 disclose an outlet valve wherein a shaft that moves up or down and is covered by a diaphragm bellows thereby engages or disengages a round inlet opening, thereby closing or opening the valve opening surrounding the inlet. The aseptic nature of the valve involves isolation of contaminants by way of a double axial seal and also its self-draining nature. However, the diaphragm valve does not have a multiple-port capability.
U.S. Pat. No. 5,273,075 (Skaer) discloses a diaphragm-based diverter valve with a single inlet and two outlets. The diaphragm engages a weir to open or close a fluid path. Stems are compressed against the diaphragms to close them against the weirs, or opened to create a fluid flow path. According to the patent, dead legs are eliminated in this design.
It is clear that valve designs for sanitizing slider or rotary valves in place without the need for disassembly have not been described in the prior art. In order for the advantages of rotary valve-based separations to be applied to process-scale manufacture of pharmaceuticals, it is mandatory to provide sanitizing means for ensuring removal of contamination within the wetted surfaces of the valve following use, without the need for disassembly. Therefore, there is a need for sanitizable rotary valves which may be intermittently flushed and cleaned, while maintaining the sterile condition of the process system.